This project concerns regulation of food intake and body weight as these pertain to obesity, and consists of the following components: (1) Further validation of conditioned salivation as a measure of appetite and hunger. (2) Use of conditioned salivation as a means of studying satiety mechanisms believed to be important; these studies include investigation of possible separate mechanisms involved in proteins, fat, and and carbohydrate metabolism, and; obese-nonobese differences in the functioning of these mechanisms. (3) Investigation of the acquisition of anticipatory control of food intake by sensory qualities of food through a process of conditioning; learning of preferences for foods eaten under conditions of high levels of hunger drive; and aversion learning under the special conditions which follow intestinal by-pass surgery. (4) Investigation of alternations in hunger and appetite as a result of weight loss which may operate to "defend" body weight. (5) Study of caloric regulation, hunger and appetite, spontaneous activity and patterns of parental reinforcement of activity level in obese and non-obese children. (6) Development of set measures of parameters of food regulation and energy expenditure in infants, with special attention to assessment of factors which would be expected to be predictors of later adiposity. BIBLIOGRAPHIC REFERENCES: Wooley, O.W.; Wooley, S.C.; Williams, B.S. (1976) Salivation as a measure of appetite: Studies of the anorectic effects of calories and amphetamine. In: D. Novin, W. Wywicka, G. Bray (Eds.), Hunger: Basic Mechanisms and Clinical Implications. New York: Raven Press. Wooley, O.W.; Wooley, S.C.; Dunham, R.B. (1976) Deprivation, expectation and threat: Effects on salivation in the obese and nonobese. Physiology and Behavior (in press).